Add wxOVERRIDE and use it in common and wxOSX code.

Make overriding virtual methods more explicit and enable additional checks
provided by C++11 compilers when "override" is used.

Closes #16100.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76173 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/logg.cpp

@@ -448,7 +448,7 @@ public:
     virtual ~wxLogFrame();
 
     // Don't prevent the application from exiting if just this frame remains.
-    virtual bool ShouldPreventAppExit() const { return false; }
+    virtual bool ShouldPreventAppExit() const wxOVERRIDE { return false; }
 
     // menu callbacks
     void OnClose(wxCommandEvent& event);